Method of manufacturing pressed concrete



Aug. 24, 1965 YUTAKA TSUDA METHOD OF MANUFACTURING PRESSED CONCRETEFiled D60. 4, 1961 2 B m h m. w W r 0 d w 7 .m 9 e 5 g m A D. m c 3INVENTOR Yurclka Tsudcl BY [/Mrfifi {iv/WM ATTORNEYS United StatesPatent 3,292,737 METHOD OF MANUFACTURING PRESSED CONCRETE Yutaka Tsuda,Setagaya-ku, Tokyo, Japan, assignor to Yawata Iron & Steel Co., Ltd,Tokyo, Japm Filed Dec. 4, 1961, Ser. No. 156,692 2 Claims. (Cl. 264-71)This invention relates to a method of manufacturing pressed concrete.

Civil engineering works in which very strong concrete sheets, piles,beams and ties are used have recently increased so greatly that it isrequired to continuously massproduce them in a streamlined operation.However, it is usual that the strength of concrete will not come outunless a considerable time is taken. Therefore, a special considerationis further required in order to improve the strength within a short timeand to manufacture structures requiring a high strength such as ironreinforced pressed concrete piles.

The present invention has solved those points mentioned above.

An object of the present invention is to provide a method ofmanufacturing iron reinforced pressed concrete sheets, piles and thelike of high strength continuously within a short time while improvingthe strength.

FIGURE 1 of the accompanying drawings is a perspective view of amanufacturing apparatus for carrying out the method according to thepresent invention.

FIGURE 2 is a comparative diagram of compressive strength tests.

The present invention shall be detailed in the follow- First of all, anassembled iron reinforcement is made by cutting steel bars into properlengths, assembling them and welding or jointing them at the respectivecontact points and said reinforcement is positioned in a molding boxwhich is easy to assemble and disassemble. Concrete which is mixed andkneaded to such hardness as will make the concrete easily flow throughsaid assembled iron reinforcement and into the corners of the moldingbox and which is not likely to make clearances or uneven parts is pouredinto the molding box by a fixed measured amount, is made uniform on thewhole by means of a vibrator, and is finished so that the height of thesurface may be constant and is covered with a lid.

Then the concrete in the molding box is molded under a strong pressureby means of a pressure oil device. In the light of experiments, a methodof pressing in two steps in which preparatory pressure of about kg./cm.is first applied and then the pressure is elevated to about 20 kg./cm.and is preferably applied continuously. That is to say, by thepreparatory pressing, the concrete mass packed in the molding box andnot yet hardened is made horizontal at a fixed height and the more orless irregular surface thereof is made smooth. Therefore, when a furtherhigher pressure is applied, the pressure distribution will be able to beeasily made uniform. F urther, as any quick pressure is avoided, theposition of the axis of the prestressed steel bar or the assembled ironreinforcement can be stabilized, water in the concrete can be made tofloat up in the direction of the pressure and thus water can beprevented from remaining in the concrete. When the concrete mass in themolding box is made smooth by the preparatory pressing, the pressure isfurther elevated to about 20 kg./cm. This predetermined pressure isapplied uniformly to each part of the long concrete mass for 6 to 8minutes by means of the same oil pressure device. The amount of waterwhich remains in the concrete after the compression has been finished,is about 23%.

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The compressing device is so arranged that the compressed state of theconcrete may be kept as the pressure being applied after the pressingforce is released.

Then the molding box and the upper lid are integrally fastened togetherso that the density of each part of the compressed concrete mass may beuniform. The molding box containing the compressed concrete mass isremoved from the pressing device and transferred to the steam curingchamber in order to carry out the curing of the concrete mass in thecompressed state as the pressure is being applied. The highest steamcuring temperature of ordinary concrete is said in literature to beabout 60 C. But, in this case, the temperature of steam may be elevatedto C. The temperature rise in such case is for 5 to 10'minutes and iskept for about 2 hours and 30 minutes. The concrete compressed and heldin the molding box will begin to harden quickly due to external heat.

The apparatus for carrying out the above described pressing moldingshall be explained with reference to the drawings.

A molding box consisting of side wall members made of steel channel 10,a bottom steel plate 12 and bottom members made of steel channel 13 iscovered with a lid consisting of cover members made of channel steel 8and ceiling steel plate 9. Several fixed stands 7 having inclined uppersurfaces on the right and left are provided on the upper surface of saidlid in a certain distance respectively. Several frames 5 whichcorrespond to said fixed stands in number, are arranged over saidmolding box. A pair of cotters 6 is fitted between each fixed stand andeach frame 5. The angles of inclination of said each stand and saidcotters are so arranged that the horizontal component of the stationaryfrictional forces may be larger than the horizontal component of theslipping force of said cotters, so that the cotters may not slip back tothe position where they had stood before they were pushed, even if thepushing from the both sides is released. Each frame 5 is so formed as tobe able to be easily disassembled by pulling out the cotters on bothsides. On both sides of the frame 5 are arranged oil pressure cylinders3. Push rods 4 of the molding box are pushed with the piston rods of theoil pressure cylinders 3 so that the cotters 6 may approach each otherfrom both sides. To each oil pressure cylinder 3 are connected apressure oil feeding pipe 1 and a return oil pipe 2. Said pressure oilfeeding pipe 1 and return oil pipe 2 are connected to an oil pressurepump 16 and an oil storage tank 18 through a switching valve 15. Betweenthe oil pressure pump 16 and the switching valve 15 are provided anaccumulator 17 and a pressure regulating valve 14 so as to make thepressure in all the cylinders uniform.

Now, if concrete 11 kneaded at a proper mixing ratio is poured in themolding box, is pounded and vibrated so that there may be no clearanceand uneven part but the whole may be uniform and is covered with thelid, the frames 5 are assembled, the cotters 6 are fitted, the push rods4 are set against the cotters, the piston rod of the oil pressurecylinder 3 is set against each push rod and a pressure oil of apredetermined pressure is fed to the pressure oil feeding pipe 1 of eachcylinder through the switching valve 15 by operating the oil pressurepump 16, each cylinder will push the cotter with a uniform pressure anda pressure will be applied to the concrete 11. In case the pressureresistance in a part of the concrete 11 is low, the pressure oil will befed into the cylinder of that part so that the whole may press theconcrete with a predetermined uniform pressure. Thus, however long orwide the concrete may be, it will be compressed in each part uniformlyunder a predetermine pressure for a fixed time. When the molding boxwith this pressure as applied is conveyed to a curing chamber and iscured, very strong pressed concrete will be made. Further, in thepresent invention, the pressure oil pipe and the oil pipe connected toeach cylinder are in common, the oil pressure fed to all the cylindersis regulated to be constant as desired through the pressure regulatingvalve provided near the oil pressure feeding source and, even when thereis any fluctuation of the oil pressure, the pressure will be directlykept constant in response to the fluctuation. Therefore, the concreteproduce will be cured under a uniform pressure on the whole surface andwill be able to form a product having no weak points.

According to the present invention, assembled iron reinforcements orprestressed steel bars are set in such molding box as is describedabove, mixed and kneaded concrete having such softness as will produceno clearance behind the iron reinforcements and in the corner parts ofthe molding box is poured into the molding box, the lid is mounted onthe concrete, a pressure is thus applied to the concrete for a fixedtime so that the density may be high, any unstable aggregate may bestabilized and excess water may be squeezed out to make the Watercontent best adapted to obtain the maximum strength in steam curing, theconcrete while still under pressure is cured with steam and is, asrequired, taken out of the moulding box and cured in water.

The strength of the pressed concrete according to the present inventionis much higher than that of the ordinary concrete. The comparativediagram is as shown in FIGURE 2. There are shown results that thepressed concrete according to the present invention has a strength morethan twice as high as that of ordinary concrete and is superior in wearstrength tests.

The method of the present invention can be applied to the manufacturerof piles, beams, ties, pillars, plates and the like.

What I claim is:

1. A method of manufacturing pressed concrete of high strength,comprising the steps of placing a mass of concrete in a mold having atleast one part thereof movable into the interior of the mold, vibratingthe mass of concrete in the mold for insuring even distribution of theconcrete in the mold, mechanically applying pressure to the movable partof the mold for moving it into the mold and thereby applying a pressureof about kg./cm. to the concrete in the mold, then increasing themechanical pressure to about kg./cm. for about 6-8 minutes and reducingthe water content of the concrete in the mold to about 23% by squeezingout excess water, and then while still maintaining said mechanicalpressure of about 20 kg./cm. applying steam to the exterior of the moldto heat the concrete within the mold to about C. in order to cure theconcrete.

2. A method of manufacturing pressed concrete of high strength,comprising the steps of placing a mass of concrete in a mold apparatushaving at least one part thereof movable into the interior of the moldand having means for holding the movable part in position after a forcehas been applied to it to apply pressure to concrete within the moldapparatus, vibrating the mass of concrete in the mold for insuring evendistribution of the concrete in the mold, applying a force to themovable mold part through said holding means for moving the movable moldpart into the mold and thereby applying a pressure of about 10 kg./cm.to the concrete in the mold, then increasing the force until thepressure on the concrete is about 20 kg./cm. and holding the pressurefor about 6-8 min. and reducing the water content of the concrete in themold to about 23% by squeezing out excess water, and then with theholding means holding the pressure on the movable mold part and thus onthe concrete in the mold, placing the mold apparatus in a steam curingchamber and filling the steam chamber with steam at 100 C. for heatingthe mold apparatus to cure the concrete.

References Cited by the Examiner UNITED STATES PATENTS 840,990 1/07Chailly 25-84 961,046 6/10 Turley 25--84 1,327,710 1/20 Hemstreet 25-1021,514,936 11/24 Seifert 264-82 1,599,413 9/26 Harrison 264-82 2,311,3582/43 Baily 25155 2,336,982 12/43 Cremer. 2,433,265 12/47 Denning.2,437,003 3/48 Ruegy 2584 2,476,653 7/49 Elberty 2583 2,585,193 2/52Vesper 2584 2,622,303 12/52 Wilson 26482 3,034,192 5/62 Maillard 25154FOREIGN PATENTS 100,076 1/ 37 Australia.

ROBERT F. WHITE, Primary Examiner. ALEXANDER H. BRODMERKEL, Examiner,

1. A METHOD OF MANUFACTURING PRESSED CONCRETE OF HIGH STRENGTH,COMPRISING THE STEPS OF PLACING A MASS OF CONCRETE IN A MOLD HAVING ATLEAST ONE LPART THEREOF MOVABLE INTO THE INTERIOR OF THE MOLD, VIBRATINGTHE MASS OF CONCRETE IN THE MOLD FOR INSURING EVEN DISTRIBUTION OF THECONCRETE IN THE MOLD, MECHANICALLY APPLYING PRESSURE TO THE MOVABLE PARTOF THE MOLD FOR MOVING IT INTO THE MOLD AND THEREBY APPLYING A PRESSUREJOF ABOUT 10 KG./CM.2 TO THE CONCRETE IN THE MOLD, THEN INCREASING THEMECHANICAL LPRESSURE TO ABOUT 20KG./CM.2 FOR ABOUT 6-8 MINUTES ANDREDUCING THE WATER CONTENT OF THE CONCRETE IN THE MOLE TO ABOUT 23% BYSQUEEZING OUT EXCESS WATER, AND THEN WHILE STILL MAINTAINING SAIDMECHANICAL PRESSURE OF ABOUT 20 KG./CM.2 APPLYING STEAM TO THE EXTERIOROF THE MOLD TO HEAT THE CONCRETE WITHIN THE MOLD TO ABOUT 100*C. INORDER TO CURE THE CONCRETE.